Introduction to domestic RF chip knowledge

Release time: 2022-09-05

Strictly speaking, domestic RF chips generally refer to chips that transmit and receive RF signals. In mobile phones, they are approximately equivalent to baseband chips. But signal transceiver and modulation and demodulation are two necessary links, so put the above two functions together into one chip, which is the baseband chip. The baseband chip is small in size and low in power consumption.

In the mobile phone terminal, the domestic RF chip is responsible for RF transceiver, frequency synthesis, and power amplification; while the baseband chip is responsible for signal processing and protocol processing. Simply put, the RF chip acts as a transmitter and a receiver. The baseband chip is the core part of the entire mobile phone, just like the host of a computer.

Radio frequency (RF) is the abbreviation of Radio Frequency, which represents the electromagnetic frequency that can be radiated to space, and the frequency range is between 300kHz and 300GHz. Radio frequency is radio frequency current, referred to as RF, which is the abbreviation of high frequency alternating electromagnetic wave. The alternating current that changes less than 1,000 times per second is called low-frequency current, and the one that changes more than 10,000 times is called high-frequency current, and radio frequency is such a high-frequency current. Radio frequency (300K-300G) is a higher frequency band of high frequency (greater than 10K), and microwave frequency band (300M-300G) is a higher frequency band of radio frequency.

The domestic radio frequency chip refers to an electronic component that converts radio signal communication into a certain radio signal waveform and sends it out through antenna resonance. The RF chip architecture includes two parts: the receiving channel and the transmitting channel. For the existing GSM and TD-SCDMA modes, if the terminal supports an additional frequency band, its radio frequency chip will add a receiving channel accordingly, but whether a new transmitting channel needs to be added depends on the relationship between the new frequency band and the original frequency band. Certainly. For a mobile communication system with receive diversity, the number of radio frequency receive channels is twice the number of radio frequency transmit channels. This means that the more the number of LTE frequency bands supported by the terminal, the number of receiving channels of its radio frequency chip will increase significantly. For example, if M frequency bands in GSM or TD-SCDMA mode are added, the number of RF chip receiving channels will increase by M; if M frequency bands in TD-LTE or FDD LTE mode are added, the number of RF chip receiving channels will increase. 2M pieces. Compared with 2G/3G, the LTE spectrum is more fragmented. In order to realize international roaming through FDD LTE, the terminal needs to support more frequency bands, which will lead to the challenge of increasing the cost and volume of the radio frequency chip.

In order to reduce the chip area and chip cost, one receiving channel of the domestic RF chip can support multiple adjacent frequency bands and multiple modes. When the terminal needs to support multiple frequency bands contained in this receiving channel, it is necessary to add switching devices in the RF front-end to adapt to the receiving SAW filter or duplexer corresponding to the multiple frequency bands, which will lead to an increase in the size and cost of the RF front-end. At the same time, the introduction of the switch will also reduce the RF performance of the receiving channel. Therefore, how to balance the contradiction between the domestic RF chip and the RF front-end in terms of volume and cost will be related to the volume and cost of the entire terminal.

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